Recoverable assembly and method of enclosing an elongated substrate using such an assembly

ABSTRACT

A recoverable assembly for enclosing a substrate has an elastic sleeve mounted in a radially stretched condition on a hold-out member that extends therebeyond at one end of the sleeve. The hold-out includes a plurality of regions of weakness extending circumferentially there around and discretely spaced apart along the length thereof such that it may be pulled back through itself to facilitate recovery of the sleeve on the substrate.

This invention relates to a recoverable assembly and its method of use,for recovering a stretched sleeve onto a substrate.

Arrangements are known for holding an elastic, typically elastomeric,sleeve in a stretched condition after manufacture until it is requiredto be recovered in use onto a substrate. One example of such an assemblyis disclosed in U.S. Pat. No. 3,515,798 (Minnesota Mining andManufacturing Company), in which an elastic tubular cover member issupported in a stretched condition on an easily removable one piecerigid helical core having interconnected adjacent coils. Uncoiling ofthe helix and removal of the core as a continuous narrow strip throughthe remainder of the helix permits the cover to be recovered onto asubstrate disposed therewithin.

EP-A-0117092 (Minnesota Mining and Manufacturing Company) discloses amodification of U.S. Pat. No. 3,515,798, in which the hollow tubularcore for supporting the elastic tubular cover member comprises acylindrical plastic tube having a plurality of circumferentially spaced,axially extending lugs on the inner wall of the tube and a continuoushelical cut extending into the wall of the tube from the exteriorsurface thereof, severing the tube into a continuous narrow strip suchthat only the lugs are connected axially along the length of the tube.

U.S. Pat. No. 5,087,492 (Societa Cavi Pirelli S.p.A.) discloses astretched elastic sleeve that is mounted on a tubular supporting bodyformed by a helically wound tape with contiguous turns. The tape hastransversely extending notches in the inner surface thereof to improvethe bendability of the tape. After the assembly of the sleeve and thebody is disposed around a substrate, an electric cable joint, the tapeis pulled out of the sleeve, permitting the sleeve to contract and toengage the cable.

U.S. Pat. No. 5,560,969 (Pirelli Cavi S.p.A) discloses a further tubularsupporting element for supporting an elastic sleeve, in which the wallof the element has a groove or incision directed along a helical lineand which has a radial depth from the outer surface of the supportingelement less than the radial thickness of the supporting element.

The stretched elastic sleeve-supporting member of each of theabove-mentioned publications comprises a strip of material that ishelically wound so as to form a tubular support member. In operation,the supported sleeve is positioned around the substrate to be covered,which may be a joint between electric cables, or a termination of such acable, and one end of the strip is grasped and pulled back through thesupporting member through the annular region between the supportingmember and the substrate. As the strip is pulled out from within theelastic sleeve, the sleeve then recovers down onto the substrate.However, with such a hold-out assembly of the elastic sleeve, theoperator has continually to pull the strip around the circumference ofthe substrate due to its helical winding within the sleeve. Furthermore,for a typical 400 mm length of the elastic tube, a strip length of theorder of 10 meters has to be provided to form the rigid helicalhold-out. It will be appreciated that the helical unwinding of thehold-out strip around the substrate for a length of about 10 meters, oreven more, can be very inconvenient, particularly bearing in mind theinherent rigidity that is required for the material of the hold-outtape. Such helical hold-outs are usually manufactured as a linear stripthat is then formed into a helical tube. It has been found that asignificant helical imprint remains on the inner surface of the elasticsleeve following withdrawal of the hold-out member. The development ofsuch an imprint is exacerbated by the time that the elastic sleevespends on the hold-out after it is pre-stretched and mounted thereonduring manufacture, and stored prior to its release in use onto asubstrate.

It is one object of the present invention to provide an assemblycomprising a stretched elastic sleeve and a tubular hold-out member thatovercomes, or at least alleviates the disadvantages with knownassemblies.

In accordance with one aspect of the present invention, there isprovided an assembly comprising an elastic sleeve mounted in a radiallystretched condition on a tubular member that extends therebeyond at oneend of the sleeve, wherein the tubular member includes a plurality ofregions of weakness extending circumferentially therearound anddiscretely spaced apart along the length thereof.

Thus, in accordance with the present invention, a series ofcircumferential discrete regions of weakness allow the tubular hold-outmember to remain in its tubular form as it is pulled back throughitself. During this step, the hold-out member may be extended in lengthby a factor of 20% to 200% depending on design details, but thisextension is significantly smaller than that obtained with existinghelical hold-outs, so that the operator can conveniently pull thetubular member around the substrate so as to recover the sleevethereonto. During the recovery process of the sleeve onto the substrate,the tubular member becomes stretched and has the form of a plurality ofgenerally cylindrical rings interconnected by cylindrical hinges, thusgenerally retaining its tubular configuration throughout the recoveryprocess.

Preferably the tubular member is of substantially right-cylindricalconfiguration, and the regions of weakness extend circumferentiallysubstantially perpendicularly to the longitudinal axis thereof.

Advantageously, each region of weakness extends substantiallycontinuously around the tubular member.

The regions of weakness may comprise indentations extending into thewall of the tubular member. Indentations may extend from the innersurface only, or from the outer surface only, or, preferably, from bothsurfaces. In the latter configuration, indentations from each surfacemay alternate along the length of the tubular member, and it isenvisaged that a few, for example two, indentations from one surface,preferably the inner surface, may alternate with one indentation fromthe outer surface.

In an alternative configuration, the regions of weakness may be providedby the tubular member being of convoluted configuration.

The regions of weakness, for example indentations, or slits, may extenda different length longitudinally of the tubular member depending onwhether they extend from the inner or from the outer surface.Advantageously, the inner regions of weakness are longer than the outerregions of weakness.

The regions of weakness may effectively divide the tubular hold-outmember longitudinally, into a plurality of contiguous rings, the numberof rings being dependent on the length of the sleeve and thus of thetubular member. However, typically there may be more than fifty suchrings, and as many as sixty or seventy for a sleeve of 400 mm length.

The ratio of the depth of the regions of weakness transversely to thelength of the tubular member to the separation of the regions ofweakness longitudinally of the tubular member is at least 1:1, and maybe 2:1, or more. However, it is also envisaged that this ratio may be aslow as 1:3.

Whilst, in order to release the tubular member from inside the stretchedsleeve when the assembly is disposed around an elongate substrate, thetubular member extends beyond the sleeve at at least one end thereof, itis preferable that the extension is at least equal to the length of thetubular member holding out the sleeve, so that the extension can bedirected from the end back through the tubular member so as to allow itto be grasped beyond the other end of the tubular member thereby tofacilitate inverting the tubular member and pulling it back throughitself so as progressively to release the elastic sleeve down onto thesubstrate.

Advantageously the tubular member comprises a thermoplastic material orblends thereof, including cross linked thermoplastic material. Suitablematerials are polypropylene (PP), polyethylene (PE),acrylonitrilebutadienestyrene (ABS),polypropylene/ethylenepropylenediene monomer (PP/EPDM) and cross-linkedpolyethylene (V-PE).

The tubular hold-out member should, in general, be of such aconfiguration and constructed of such a material that allows itsdeformation and/or cracking to facilitate it being inverted andwithdrawn back through itself. That is to say, it must be able to changefrom a state of being mechanically stable with regards to radialpressure, to one in which, whilst retaining a generally tubular shape,it can be inverted and reduce in diameter for withdrawal through itself;the regions of weakness allow this to occur. It will be appreciated,however, that the material of the tubular member has to be selectedappropriately. Thus, the more rigid the material is, the thinner thewall thickness must be.

The tubular member may be formed by a moulding process, for exampleinjection moulding or blow moulding, or by an extrusion process.

The elastic sleeve of the assembly is preferably made of an elastomer orrubber, preferably silicone or ethylenepropylenediene monomer (EPDM).

The sleeve may be provided as a single layer, or as two or more separateor integrated layers, which may or may not be co-terminous. In thelatter case, different layers may have different mechanical and/orelectrical properties as required to suit the substrate and theenviromnent. One of the layers could, for example, be a mastic or amesh, for example of metal.

In accordance with another aspect of the present invention, there isprovided a method of enclosing an elongate substrate using an assemblyaccording to any one of the preceding claims, wherein the assembly ispositioned around the substrate with the stretched sleeve longitudinallydisposed over its final required position with the extension of thetubular member located invertedly in the annular region between thetubular member and the substrate, wherein, whilst maintaining the sleevein its required position, the free end of the extension is pulled so asto invert the tubular member supporting the sleeve and to withdraw itthrough itself along the annular region until it is completely removedfrom the sleeve, thereby allowing the sleeve progressively to recoverradially onto the substrate.

Although the present invention may be used to recover a suitable elasticsleeve onto any substrate as required, it does find particular advantagein electrical applications, where the sleeve can be recovered onto, forexample, a splice between electrical cables, or over the termination ofan electrical cable. To this end, the sleeve may be provided withelectrical insulating, conductive, semi-conductive, or stress gradingand/or weather resistant properties as required.

Embodiments of an assembly and its method of use, each in accordancewith the present invention, will now be described, by way of example,with reference to the accompanying drawings, in which:

FIG. 1 is a schematic section through a first embodiment of an elasticsleeve mounted on a tubular hold-out member;

FIG. 2 is an enlarged section of the region A of FIG. 1;

FIG. 3 shows a position in the application of the assembly of FIG. 1with the sleeve partially recovered onto a substrate;

FIG. 4 is a detail of the region B of FIG. 3;

FIG. 5 is a section through a portion of a second embodiment of thetubular member of the assembly as moulded;

FIG. 6 is a section corresponding to that of FIG. 5 after the tubularmember has been subjected to a longitudinal compression prior tomounting of the stretched sleeve thereon;

FIG. 7 is a section through a portion of a third embodiment of thetubular member of the assembly as moulded;

FIG. 8 is a section corresponding to that of FIG. 7 alter the tubularmember has been subjected to a longitudinal compression prior tomounting of the stretched sleeve thereon;

FIG. 9 is a section through a fourth embodiment of the tubular member ofthe assembly as moulded;

FIG. 10 is a schematic section through a portion of a fifth embodimentof the tubular member of the assembly as moulded;

FIG. 11 is a schematic section through a portion of a sixth embodimentof the tubular member of the assembly as moulded;

FIG. 12 is a schematic section through a portion of a seventh embodimentof the tubular member of the assembly as moulded;

Referring to FIGS. 1 to 4, an assembly comprises a cylindricalelastomeric sleeve 2 that is retained in a radially expandedconfiguration on a rigid right-cylindrical hold-out member 4. Thehold-out member 4 comprises a first, outer portion 6 that supports thesleeve 2, and, contiguous therewith, an inner portion 8 that is foldedback at one end of the sleeve 2, passes within the tubular member outerportion 6 and then emerges from the other end of the assembly.

As can be seen in FIG. 2, the hold-out member 4 has rectangular slitsextending thereinto at longitudinally spaced apart locations, with afirst set of slits 10 extending from the inner surface and a second setof slits 12, alternating therewith, extending from the outer surface.The slits 10 and 12 extend continuously circumferentially around thetubular member 4 in planes that are substantially perpendicular to thelongitudinal axis 14 of the assembly.

Referring specifically to FIGS. 3 and 4, the assembly is shown after ithas been slid into position over a cylindrical substrate 16. As shown,the inverted free end 9 of the inner portion 8 of the hold-out member 4is being pulled so as to bring about progressive inversion of the outertubular portion 6, with the result that as the portion 6 isprogressively withdrawn, the sleeve 2 recovers radially onto the surfaceof the substrate 16. Complete withdrawal of the hold-out member 4 inthis way will result in the entire length of the sleeve 2 recoveringinto close conformity with the substrate 16.

FIG. 4 shows how the inversion and withdrawal of the hold-out member 4is facilitated by the presence of the circumferential slits 10 and 12,the arrows X indicating the direction of movement of the hold-outmember, and the arrows Y indicating the direction of recovery of thesleeve 2.

Thus, as the inner tubular member portion 8 is pulled in the direction Xit peels away from the sleeve 2, and the inner slits 10 allow thetubular member 4 to compress as it inverts, the inversion beingfacilitated by the outer slits 12 allowing the tubular member 4 tostretch upon inversion, with the slits 10 and 12 remaining stretched asthe inner portion 8 is then withdrawn through the annular region betweenthe rigid portion of the member 4 and the substrate 16.

FIG. 5 shows a section through the wall of a further embodiment of atubular hold-out member 20 which has been formed in a mould so as to beof convoluted configuration with a set of generally U-shaped outertroughs 22 alternating with generally U-shaped inner troughs 24 toprovide alternating inner and outer regions of weakness extendingcircumferentially around the tubular member 20.

FIG. 6 shows the tubular member 20 after having been subject to alongitudinal compression so as substantially to close up the troughs 22and 24 so as to provide a substantially smooth outer surface for thehold-out tubular member 20 for receiving a radially stretchedelastomeric sleeve 2 thereon.

FIG. 7 shows a section through the wall of a still further embodiment ofa tubular hold-out member 30 which has been formed in a mould so as tobe of convoluted configuration with a set of outer troughs 32alternating with inner troughs 34 to provide inner and outer regions ofweakness extending circumferentially around the tubular member 30. Inthis embodiment, the innermost and outermost walls of the tubular member30 are relatively thick and are interconnected by relatively thin, andthus more flexible, side portions 36.

FIG. 8 shows the tubular member 30 after having been subject to alongitudinal compression so as substantially to close up the troughs 32and 34 so as to provide a substantially smooth outer surface for thehold-out tubular member 30 for receiving a radially stretchedelastomeric sleeve 2 thereon.

FIG. 9 shows another embodiment of tubular member 37 of convolutedconfiguration with the inner space regions 38 being wider than the outerspace regions 39. Whether longitudinal compression of the embodiments ofFIGS. 5, 7 and 9 is necessary, and to what extent, will depend on thematerial of the hold-out member and on the material of the elasticsleeve, especially on the hardness thereof. Thus, the harder a materialis selected for the sleeve, the less likely it is to deform into theopenings at the outside of the hold-out member, and the greater thelength of the openings longitudinally of the member can be. In the caseof a multi-layer sleeve, its inner or innermost layer may be of a hardermaterial than outer layer(s). In this way, deformation into the regionsof weakness of the hold-out member can be avoided, or at leastminimised, whilst still providing sufficient radially-inwards pressureto ensure full recovery onto a substrate.

Referring to FIG. 10, a tubular hold-out member 40 is shownschematically with relatively narrow slits 42 formed in its outersurface, and alternating therewith, relatively wide slits 44 in itsinner surface. This represents the preferred general configuration ofthe tubular member of the assembly of the invention. Also, this figureshows by way of example a ratio of the wall thickness H of the tubularmember to the longitudinal length W of the sections thereof betweensuccessive regions of weakness of approximately 2:1.

In the embodiment of tubular hold-out member 50 shown schematically inFIG. 11, slits 52 are shown provided only in the outer surface thereof.Also this shows that the ratio of the wall thickness H to the “ring”width W is approximately 1:1.

In a further embodiment of tubular member 60 shown schematically in FIG.12, slits 62 in the outer surface thereof are relatively short, comparedwith the slits 52 of the tube 50 (FIG. 11) whilst being spaced apart atsubstantially the same distance, giving a ratio of the wall thickness Hto the longitudinal extension W of the ring element of 1:3, for example.

It will be appreciated that each embodiment of hold-out member shown inFIGS. 10, 11 and 12 present a substantially13 smooth outer surface forreceiving the elastomeric sleeve.

1. An assembly comprising an elastic sleeve mounted in a radiallystretched condition on a hold-out member that extends therebeyond at oneend of the sleeve, wherein the hold-out member includes a plurality ofregions of weakness extending circumferentially there around anddiscretely spaced apart along the length thereof.
 2. An assemblyaccording to claim 1, wherein the hold-out member is of a substantiallyright-cylindrical configuration.
 3. An assembly according to claim 2,wherein the regions of weakness extend circumferentially substantiallyperpendicularly to the longitudinal axis of the hold-out member.
 4. Anassembly according to claim 1, wherein each region of weakness extendssubstantially continuously around the hold-out member.
 5. An assemblyaccording to claim 1, wherein the regions of weakness compriseindentations extending into the wall of the hold-out member from aninner surface thereof.
 6. An assembly according to claim 1, wherein theregions of weakness comprise indentations extending into the wall of thehold-out member from an outer surface thereof.
 7. An assembly accordingto claim 1, wherein the regions of weakness comprise indentationsextending into the wall of the hold-out member from an inner surface andfrom an outer surface thereof.
 8. An assembly according to claim 7,wherein inner surface indentations alternate with outer surfaceindentations along the length of the hold-out member.
 9. An assemblyaccording to claim 1, wherein the regions of weakness are provided bythe hold-out member being of convoluted configuration.
 10. An assemblyaccording to claim 7, wherein the regions of weakness of the innersurface and of the outer surface of the tubular member are of adifferent length longitudinally of the hold-out member.
 11. An assemblyaccording to claim 8, wherein the inner regions of weakness are longerthan the outer regions of weakness.
 12. An assembly according to claim1, wherein the regions of weakness comprise slits, of substantiallyrectangular configuration.
 13. An assembly according to claim 1 whereinthe ratio of the depth of the regions of weakness transversely to thelength of the hold-out member to the separation of the regions ofweakness longitudinally of the hold-out member is between about 1:3 andabout 2:1.
 14. An assembly according to claim 1, wherein the extensionof the hold-out member beyond an end of the elastic sleeve is such thatit is arranged to be passed back through the hold-out member to begripped from the other end, by an operator in use, so as to invert anddraw the hold-out member through itself, thus releasing the sleeve fromits stretched condition.
 15. An assembly according to claim 14, whereinthe extension of the hold-out member is at least as long as the sleeve.16. An assembly according to claim 1, wherein the hold-out membercomprises a thermoplastic material or blends thereof, includingcross-linked thermoplastic material.
 17. An assembly according to claim1, wherein the elastic sleeve comprises an elastomer or a rubber,preferably silicone or EPDM.
 18. (canceled)
 19. (canceled) 20.(canceled)
 21. (canceled)